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Re: writing a simple example in prov-o, help

From: Simon Miles <simon.miles@kcl.ac.uk>
Date: Wed, 26 Oct 2011 10:53:12 +0100
Message-ID: <CAKc1nHc4efAag3UrrVEkuBgxbBdEPFLg7T57Z6AkuBJMtX7wzQ@mail.gmail.com>
To: Provenance Working Group WG <public-prov-wg@w3.org>
Hi Paul,

I think the argument you make is the same as implied by my example...
except that the conclusion is different.

As you say, the provenance best practice could be to use permalinks.
So, in the example, the bloggers should use permalinks. They have no
control over what the original YouTube URL deferences to, so cannot
ensure it is a permalink. Unless they have special information, they
can only assume it is not, and so either they:
  (a) cannot say anything about the video at all, or
  (b) need to create their own permalink to refer to the video.
If doing (b), this new URI clearly should connect to the YouTube URL
as it is the video that the provenance is about. However, to make it
into a permalink, there must be something more which ensures it always
describes the same content, i.e. characterisation of the entity. The
provenance then looks like the PROV-OM examples rather than the simple

I'm not clear if you are arguing for option (a) in your email, i.e.
limit people to only refer to things in their provenance when they can
control those thing's immutability, but this seems very restrictive.

I'm not saying I prefer the long-winded provenance data, just that it
appears the desire for interoperability makes it necessary beyond
limited cases.

I think accounts and consistency are tangential issues - there is
nothing inconsistent in what is asserted, the inconsistency comes only
from the ambiguity of what is being asserted about.


> The point is that two different people are asserting it. We can't
> maintain consistency across the people. This is why we have accounts, no?
> I think one way to handle this is to have a best practice where we
> suggest people use permalinks (see
> http://en.wikipedia.org/wiki/Permalink) or cool-uris.  Indeed, to me
> this is probably the best way to introduce entities.
> So overall, my suggestion would be to maintain simplicity but suggest
> people use uris that refer to content that doesn't change.
> But please bring this up in interoperability page.
> cheers,
> Paul
> Simon Miles wrote:
>> Paul, all,
>> Just to properly understand why what is being discussed is important,
>> I wanted to expand your example to a larger use case.
>> At time T, you say something about a video on your blog and assert:
>> <http://thinklinks.wordpress.com/2011/07/31/why-provenance-is-fundamental-for-people/>
>> prov:wasDerivedFrom
>> <http://www.ted.com/talks/paul_bloom_the_origins_of_pleasure.html>.
>> At time T+1, the video is edited to introduce a previously missing
>> segment that undermines the message of your blog entry. The video URI
>> stays the same.
>> At time T+2, I say something about the (updated) video on my blog and assert:
>> <http://inkings.org/2011/10/08/why-provenance-is-pointless/>
>> prov:wasDerivedFrom
>> <http://www.ted.com/talks/paul_bloom_the_origins_of_pleasure.html>.
>> We could then observe:
>>   - Even if the above use case doesn't happen to you, by using the
>> simplest form of provenance you are opening the possibility of it
>> happening and you would not even know about it.
>>   - It doesn't help to say that the video owners shouldn't use the same
>> URL, because it is not under the control of either those creating or
>> consuming the provenance.
>>   - There is nothing apparently wrong with either of our assertions
>> (except the lack of characterisation), and I don't know anything about
>> your blog so don't take it into account in my blog's provenance.
>>   - It seems reasonable criteria for interoperability that if you read
>> Prov-DM from two separate sources referring to the same entity, then
>> either there is an error in (at least) one or they are mutually
>> consistent. I couldn't see what this would correspond to in the
>> interoperability discussion [1] though.
>> Thanks,
>> Simon
>> [1] http://www.w3.org/2011/prov/wiki/Interoperability

Dr Simon Miles
Lecturer, Department of Informatics
Kings College London, WC2R 2LS, UK
+44 (0)20 7848 1166
Received on Wednesday, 26 October 2011 09:53:40 UTC

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